CA1236491A - Low density phosphate bonded spinel refractories - Google Patents
Low density phosphate bonded spinel refractoriesInfo
- Publication number
- CA1236491A CA1236491A CA000491910A CA491910A CA1236491A CA 1236491 A CA1236491 A CA 1236491A CA 000491910 A CA000491910 A CA 000491910A CA 491910 A CA491910 A CA 491910A CA 1236491 A CA1236491 A CA 1236491A
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- Prior art keywords
- composition
- percent
- weight
- reactive
- calcined
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
- C04B38/02—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by adding chemical blowing agents
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/34—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing cold phosphate binders
- C04B28/342—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing cold phosphate binders the phosphate binder being present in the starting composition as a mixture of free acid and one or more reactive oxides
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
- C04B35/44—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
- C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
- C04B35/63—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B using additives specially adapted for forming the products, e.g.. binder binders
- C04B35/6303—Inorganic additives
- C04B35/6306—Binders based on phosphoric acids or phosphates
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
- C04B2111/00663—Uses not provided for elsewhere in C04B2111/00 as filling material for cavities or the like
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Structural Engineering (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Thermal Insulation (AREA)
- Porous Artificial Stone Or Porous Ceramic Products (AREA)
Abstract
ABSTRACT
Ceramic compositions having a relatively low density, thermal insulating properties, high structural strength and resilancies to chemical attack are disclosed.
These compositions can be used to produce monolithic insulating installations or insulating shapes.
Ceramic compositions having a relatively low density, thermal insulating properties, high structural strength and resilancies to chemical attack are disclosed.
These compositions can be used to produce monolithic insulating installations or insulating shapes.
Description
3L~3~
LOW DENS I TY PHOSPHATE BONDED
SPINEL REFRACTORIES
..
The present invention concerns magnesium aluminum oxide spinel compositions for use as a light weigh~ casting mold and thermal insl~lation that has high structural strength and resistancie to chemical attack.
The following patents and literature references represent some aspects of the general field of magnesium aluminum oxide spinels used in mortars, castable~ and coatings and the like employing phosphorous acids as a reactive component. U.S. Patent 3,730,744, employing fuzed magnesium aluminate, discloses an aggregate in cast shapes employing Al(H2PO4)3 as the bonding solution which contains alkalizing ions as the curing agents.
U.S. Patent 3,285,758 teaches ammonium phosphate in combination with aluminum phosphate plus MgO (calcined dolomite) where spinel is men~tioned as an aggregate.
U.S. Patent 4,341,561 teaches the production of foamed refractories using hydraulic cements, some of which also contain phosphate materials. U. S. Paten-t 4,459,156 discloses that a reactive spinel may be one of the components of the motar. The use of a non-reactive gas autogenerated compound is not 'isclosed.
3 2 , 7 7 5 -F - 1 - ~i ~ ` .
A fundamen-tal review of phosphate bonding is found in J. AMER. CERAMIC SOCIETY, Vol. 133, No. 8, August l, 1950 by William David Kingery. Another review is found in Ceramic Bulletin, Vol. 56, No. 7, page 640 by J.E. Cassidy (1977). Other studies are as follows: Ceramic Bulletin, Vol 59, No. 7 (1980) by Francisco J. Gonzales and John W. Hal:Loran, "Reaction of Orthophosphoric Acid with Several Forms of Aluminum Oxide" and an abstract of a Russian Scientific paper authored by L. B. Khoroshavin, V. ;.. Ryabin, I. E.
Sipeiko, V. N. Naumov, G. A. ~ychev, V. Ya. Pavlov, V.
M. Chyrin, N. F. Serenko, B. V. Ponomarev, and E. P.
Kosolapova, Eastern Institute of Refractories, Ural Scientific-Research Institute of Chemistry, Perm Chemical Plant, A11-Union Scientific-Research Institute for the Power Supply in Nonferrous Metallurgy, from Ogneupory, No. 3, pp. 34-36, March, 1977 (translated).
The above two review articles, the one by Kingery (covering the art to 1949) and the other by Cassidy (from 1949-1977) form a very complete picture of the state of technology on phosphate bonding.
Materials listed as forming phosphate bonds with phos-phoric acid are: Tio2, CaO, FeO, Fe2O3, Nio, ZnO, Zro2, MgO, Al2O3, and CrO3. These may be reacted as pure compounds or as constituents in mineral compositions, i.e., asbestos, bauxite or clay. The most common bonding mechanism using phosphoric acid is the reaction with alumina to form Al(H2PO4)3, which is also the starting material in many formulations in place of 3Q H3PO4. Al(E2PO4)3 further reacts with ei-ther alumina, clay or bauxite, resulting in orthophosphates (MgHPO4-3H2O or AlH3(PO4) 2 ) as the bond.
32,775-F -2-~3~
In the H3PO~ + Al2O3 system addition of Mg 2, Fe 3 or Be 2 ions increase bonding st:rength but -these ions also contribute to "premature" setting.
The patent literature very closely follows the above literature review; that is, while it teaches phosphate bonded systems, it only mentions spinel as one possible aggregate material. Also -these aggregates are not "reactive" with any activity observed due to free MgO and are typically part of the coarse grained portion with very few ~ines (material <325 mesh).
In accordance with the present invention, effective compositions can be produced to serve as -thermal insulation which have high structural strength and resis~ance ~o chemical a-ttack. These compositions can be used to produce monolithic insulating instal-lations or insulating shapes. The essential ingre-dients for producing the present compositions are (1) a reactive MgAl2O4 spinel or spinels, (2) optionally, non-reactive fillers, (3) a non-reactive gas auto-generating compound means of introducing void volume(4) aluminum acid phosphate moieties and/or phosphoric acid, (5) water, and (6) optionally, handling agents.
The present invention includes a castable composition which is particularly usable in the metals industry for construction and repair of low density or insula-ting structures, linings and component parts, for example, in melting furnaces, electroly-tic metal winning cells, component parts for metal casting machines, including transfer pipes, troughs, and the like, as well as low density refractory struc-tures in the chemical and petrochemical industry.
32,775-F -3-, ~ , , .
~3~L9~
One aspect of the present invention concerns compositions comprising:
(a) 10 to ~0 percent by weight of a reactive MgA12O4 spinel or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures and prepared by coprecipitating water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
(b) preferably, 0 to 50 percent by weight of a substantially non-reactive filler;
(c) a non-reactive gas autogenerated from 1 to 40 percent by weight of a compound whieh cleeomposes under acidic eonditions and generates gas wi-thin said composition;
(d) 1 to 20 percent by we:ight of an inorganic phosphorous compound which forms (PO3)3 moieties on heating at above about 200 C;
(e) 8 to 40 percent by weight of water; and (f) preferably 0 to 5 percent by weight of handling agents.
Aecording to another aspect of the present invention there is provided a process for producing a porous refraetory eomposition, which process comprises ~orming an aqueous suspension comprising:
(a) 10 to ~0 percent by weight of a reactive MgA12O4 spinel or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures and prepared by coprecipitating water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
~, ~36~
(b) from 1 to 40 percent by weight of a compound wllich decomposes under acidic conditions to form a gas;
(c) 1 to ~0 percent ky weight of an inorganic phosphorous compound which forms (PO3)3 moieties on heating at above about 200 C; and (d) 8 to 40 percent by weight of water, and allowing the components to react to form a porous refractory composition.
A fired refractory material is obtained by firing the above compositions to a temperature of at least 200 C.
The MgA12O4 spinels of component (a) are preferably prepared in accordance wi-th the teachings of U.S. Patent 4,400,431.
The spinels have been calcined and may be sinter~d to at least about 1600C. The preEerred spinel is a mixture where one MgA12O4 spinel has been calcined to about 900C and the other spinel at about 1600C. When only one spinel is present, preferably the spinel has been calcined to 1600 C.
The non-reactive filler of component (b) is typically highly sintered such as tabular alumina, fused grain alumina, fused grain spinel (MgA12O4), highly sintered MgA12O4 (made by U.S. Patent 4,400,431), as well as other fused grain materials such as ZrSiO4.
The non-reactive gas forming compound of component (c) decomposes on contact with the acidic component and generates gas to produce bubbles, which serve as void volume to reduce the fired density and give the produc-t an insulating character. The CO2 producing agent may b~ any acid decomposable carbonate such as dolomite or magnesium carbonate. While other "'"~
~3~
alkali metal or alkaline earth metal carbonates may be employed they introduce components which may degrade the physical properties of the casting. One way to avoid these problems is -to use a MgAl(HCO3) OH (x ~ y to balance positive valence) compGund prepared in accordance with U.S. Patent 4,400,431. Preferred compounds are dolomite and MgAl(OH)4.5 (HCO3~0.5.
The inorganic phosphorous compound of component (d) should be capable of forming (PO3)3 moieties on heating, i.e.
on drying out of the formulation, a-t above about 200 C.
10 Preferred phosphorous compounds are A~(H2PO4)3 and H3PO4.
Water is employed in component (e) as necessary to give workability to the binder composition, as are handling agents and other modi:Eiers o:E componen-t (f). Total water conten-t usually employed. is :Erom about 8 to about 40 weight percent of th~ total composition.
Handling agents, including set modifiers, of component (f) suitable for use herein include activated alumina, fumed alumina (Al2O3), glycerine, polyvinyl alcohol, MgO, Mg(OH)2, MgO/MgAl2O4 mixtures or mixtures of two or more, employed in from 0 to about 5 weight percent of the total composition. Other well-known handling agents may be employed.
-5a-.`~
~3~
In the following examples, unless otherwise denoted, the reactive MgAl2O4 spinel is derived from a coprecipitation process in which a mixture of magnesium aluminum hydroxides (MgxAly(OH)z) and aluminum hydrox ides and/or aluminum oxyhydroxides are produced and thereafter calcined to between about 700C and about 1650C. The magnesium aluminum hydroxide phase repre-sented a~ove may contain other anions partially substi-tuting for hydroxide (e.g. Cl , NO3 , S04 , CO3 ), the presence and amount of which will be determined by the typ~ of reactant salts used in the coprecipitation and the type and duration of subsequent treatments, chemical or thermal, to which the precipitate phase has been subjected. The precipitate of ma~nesium/aluminum and aluminum hydroxy compounds is referred to as spinel precursor. The overall A1/Mg ratio with this mi~-ture will be very nearly 2.0, unless otherwise noted. If this ratio significantly deviates from 2.0 (e.g. <1.90 or >2.10) segregated MgO and/or Al 23 phases are normally observed in the calcined or sintered product and these can affect reactivity.
The Al(H2PO4)3, H3PO~, fused grain Al 23' fumed alumina, porous alumina, and fibrous alumina are all commercially available, s~ubstantially pure compounds and/or solutions. The sintered spinels may be commer-cially available fused grain material or a highly sintered, (above 1650C), spinel prepared in accordance with U.S. Patent 4,400,431.
Formulations may consist of two main parts.
The binder phase, produced by reacting an acidic phos-phate species with at leas-t one active oxide species, is the first part. The aggregate phase, which contains 32,775-F -6-~ ~ ~ 6~ ~
the C02 producing agent, is the second part. The binder phase is often prepared out prior to the addi-tion ~f the aggregate or filler material which latter component(s) may be inert, as in the c:ase of fused grain, tabular, or fibrous Al203, or highly sintered (>1650C) MgAl204, or may have some degree of reac-tivity, as in the case of MgAl2O4 sint:ered to _I650C
or calcined Al2O3. This activity is clue to changes in surface area, degree of crystalline perfection and/or pcpulation of surface hydroxyls available for reaction.
Magnesium aluminum spinel, 7.6 g, calcined at 900C and sized to pass through a U.S. standard lO0 mesh seive was suspended in a solution of 11.8 g.
Al(H2P04)3 i.n 13.2 grams ~I20. 11.0 g. of spinel sintered at ~1600C was added and -the slurry se-t aside. In a separate container 75 grams of a mixture produced by ball milling 30 g of dolomite (MgCa(C03)2) -together with lO0 grams of magnesium aluminum spinel sintered at
LOW DENS I TY PHOSPHATE BONDED
SPINEL REFRACTORIES
..
The present invention concerns magnesium aluminum oxide spinel compositions for use as a light weigh~ casting mold and thermal insl~lation that has high structural strength and resistancie to chemical attack.
The following patents and literature references represent some aspects of the general field of magnesium aluminum oxide spinels used in mortars, castable~ and coatings and the like employing phosphorous acids as a reactive component. U.S. Patent 3,730,744, employing fuzed magnesium aluminate, discloses an aggregate in cast shapes employing Al(H2PO4)3 as the bonding solution which contains alkalizing ions as the curing agents.
U.S. Patent 3,285,758 teaches ammonium phosphate in combination with aluminum phosphate plus MgO (calcined dolomite) where spinel is men~tioned as an aggregate.
U.S. Patent 4,341,561 teaches the production of foamed refractories using hydraulic cements, some of which also contain phosphate materials. U. S. Paten-t 4,459,156 discloses that a reactive spinel may be one of the components of the motar. The use of a non-reactive gas autogenerated compound is not 'isclosed.
3 2 , 7 7 5 -F - 1 - ~i ~ ` .
A fundamen-tal review of phosphate bonding is found in J. AMER. CERAMIC SOCIETY, Vol. 133, No. 8, August l, 1950 by William David Kingery. Another review is found in Ceramic Bulletin, Vol. 56, No. 7, page 640 by J.E. Cassidy (1977). Other studies are as follows: Ceramic Bulletin, Vol 59, No. 7 (1980) by Francisco J. Gonzales and John W. Hal:Loran, "Reaction of Orthophosphoric Acid with Several Forms of Aluminum Oxide" and an abstract of a Russian Scientific paper authored by L. B. Khoroshavin, V. ;.. Ryabin, I. E.
Sipeiko, V. N. Naumov, G. A. ~ychev, V. Ya. Pavlov, V.
M. Chyrin, N. F. Serenko, B. V. Ponomarev, and E. P.
Kosolapova, Eastern Institute of Refractories, Ural Scientific-Research Institute of Chemistry, Perm Chemical Plant, A11-Union Scientific-Research Institute for the Power Supply in Nonferrous Metallurgy, from Ogneupory, No. 3, pp. 34-36, March, 1977 (translated).
The above two review articles, the one by Kingery (covering the art to 1949) and the other by Cassidy (from 1949-1977) form a very complete picture of the state of technology on phosphate bonding.
Materials listed as forming phosphate bonds with phos-phoric acid are: Tio2, CaO, FeO, Fe2O3, Nio, ZnO, Zro2, MgO, Al2O3, and CrO3. These may be reacted as pure compounds or as constituents in mineral compositions, i.e., asbestos, bauxite or clay. The most common bonding mechanism using phosphoric acid is the reaction with alumina to form Al(H2PO4)3, which is also the starting material in many formulations in place of 3Q H3PO4. Al(E2PO4)3 further reacts with ei-ther alumina, clay or bauxite, resulting in orthophosphates (MgHPO4-3H2O or AlH3(PO4) 2 ) as the bond.
32,775-F -2-~3~
In the H3PO~ + Al2O3 system addition of Mg 2, Fe 3 or Be 2 ions increase bonding st:rength but -these ions also contribute to "premature" setting.
The patent literature very closely follows the above literature review; that is, while it teaches phosphate bonded systems, it only mentions spinel as one possible aggregate material. Also -these aggregates are not "reactive" with any activity observed due to free MgO and are typically part of the coarse grained portion with very few ~ines (material <325 mesh).
In accordance with the present invention, effective compositions can be produced to serve as -thermal insulation which have high structural strength and resis~ance ~o chemical a-ttack. These compositions can be used to produce monolithic insulating instal-lations or insulating shapes. The essential ingre-dients for producing the present compositions are (1) a reactive MgAl2O4 spinel or spinels, (2) optionally, non-reactive fillers, (3) a non-reactive gas auto-generating compound means of introducing void volume(4) aluminum acid phosphate moieties and/or phosphoric acid, (5) water, and (6) optionally, handling agents.
The present invention includes a castable composition which is particularly usable in the metals industry for construction and repair of low density or insula-ting structures, linings and component parts, for example, in melting furnaces, electroly-tic metal winning cells, component parts for metal casting machines, including transfer pipes, troughs, and the like, as well as low density refractory struc-tures in the chemical and petrochemical industry.
32,775-F -3-, ~ , , .
~3~L9~
One aspect of the present invention concerns compositions comprising:
(a) 10 to ~0 percent by weight of a reactive MgA12O4 spinel or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures and prepared by coprecipitating water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
(b) preferably, 0 to 50 percent by weight of a substantially non-reactive filler;
(c) a non-reactive gas autogenerated from 1 to 40 percent by weight of a compound whieh cleeomposes under acidic eonditions and generates gas wi-thin said composition;
(d) 1 to 20 percent by we:ight of an inorganic phosphorous compound which forms (PO3)3 moieties on heating at above about 200 C;
(e) 8 to 40 percent by weight of water; and (f) preferably 0 to 5 percent by weight of handling agents.
Aecording to another aspect of the present invention there is provided a process for producing a porous refraetory eomposition, which process comprises ~orming an aqueous suspension comprising:
(a) 10 to ~0 percent by weight of a reactive MgA12O4 spinel or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures and prepared by coprecipitating water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
~, ~36~
(b) from 1 to 40 percent by weight of a compound wllich decomposes under acidic conditions to form a gas;
(c) 1 to ~0 percent ky weight of an inorganic phosphorous compound which forms (PO3)3 moieties on heating at above about 200 C; and (d) 8 to 40 percent by weight of water, and allowing the components to react to form a porous refractory composition.
A fired refractory material is obtained by firing the above compositions to a temperature of at least 200 C.
The MgA12O4 spinels of component (a) are preferably prepared in accordance wi-th the teachings of U.S. Patent 4,400,431.
The spinels have been calcined and may be sinter~d to at least about 1600C. The preEerred spinel is a mixture where one MgA12O4 spinel has been calcined to about 900C and the other spinel at about 1600C. When only one spinel is present, preferably the spinel has been calcined to 1600 C.
The non-reactive filler of component (b) is typically highly sintered such as tabular alumina, fused grain alumina, fused grain spinel (MgA12O4), highly sintered MgA12O4 (made by U.S. Patent 4,400,431), as well as other fused grain materials such as ZrSiO4.
The non-reactive gas forming compound of component (c) decomposes on contact with the acidic component and generates gas to produce bubbles, which serve as void volume to reduce the fired density and give the produc-t an insulating character. The CO2 producing agent may b~ any acid decomposable carbonate such as dolomite or magnesium carbonate. While other "'"~
~3~
alkali metal or alkaline earth metal carbonates may be employed they introduce components which may degrade the physical properties of the casting. One way to avoid these problems is -to use a MgAl(HCO3) OH (x ~ y to balance positive valence) compGund prepared in accordance with U.S. Patent 4,400,431. Preferred compounds are dolomite and MgAl(OH)4.5 (HCO3~0.5.
The inorganic phosphorous compound of component (d) should be capable of forming (PO3)3 moieties on heating, i.e.
on drying out of the formulation, a-t above about 200 C.
10 Preferred phosphorous compounds are A~(H2PO4)3 and H3PO4.
Water is employed in component (e) as necessary to give workability to the binder composition, as are handling agents and other modi:Eiers o:E componen-t (f). Total water conten-t usually employed. is :Erom about 8 to about 40 weight percent of th~ total composition.
Handling agents, including set modifiers, of component (f) suitable for use herein include activated alumina, fumed alumina (Al2O3), glycerine, polyvinyl alcohol, MgO, Mg(OH)2, MgO/MgAl2O4 mixtures or mixtures of two or more, employed in from 0 to about 5 weight percent of the total composition. Other well-known handling agents may be employed.
-5a-.`~
~3~
In the following examples, unless otherwise denoted, the reactive MgAl2O4 spinel is derived from a coprecipitation process in which a mixture of magnesium aluminum hydroxides (MgxAly(OH)z) and aluminum hydrox ides and/or aluminum oxyhydroxides are produced and thereafter calcined to between about 700C and about 1650C. The magnesium aluminum hydroxide phase repre-sented a~ove may contain other anions partially substi-tuting for hydroxide (e.g. Cl , NO3 , S04 , CO3 ), the presence and amount of which will be determined by the typ~ of reactant salts used in the coprecipitation and the type and duration of subsequent treatments, chemical or thermal, to which the precipitate phase has been subjected. The precipitate of ma~nesium/aluminum and aluminum hydroxy compounds is referred to as spinel precursor. The overall A1/Mg ratio with this mi~-ture will be very nearly 2.0, unless otherwise noted. If this ratio significantly deviates from 2.0 (e.g. <1.90 or >2.10) segregated MgO and/or Al 23 phases are normally observed in the calcined or sintered product and these can affect reactivity.
The Al(H2PO4)3, H3PO~, fused grain Al 23' fumed alumina, porous alumina, and fibrous alumina are all commercially available, s~ubstantially pure compounds and/or solutions. The sintered spinels may be commer-cially available fused grain material or a highly sintered, (above 1650C), spinel prepared in accordance with U.S. Patent 4,400,431.
Formulations may consist of two main parts.
The binder phase, produced by reacting an acidic phos-phate species with at leas-t one active oxide species, is the first part. The aggregate phase, which contains 32,775-F -6-~ ~ ~ 6~ ~
the C02 producing agent, is the second part. The binder phase is often prepared out prior to the addi-tion ~f the aggregate or filler material which latter component(s) may be inert, as in the c:ase of fused grain, tabular, or fibrous Al203, or highly sintered (>1650C) MgAl204, or may have some degree of reac-tivity, as in the case of MgAl2O4 sint:ered to _I650C
or calcined Al2O3. This activity is clue to changes in surface area, degree of crystalline perfection and/or pcpulation of surface hydroxyls available for reaction.
Magnesium aluminum spinel, 7.6 g, calcined at 900C and sized to pass through a U.S. standard lO0 mesh seive was suspended in a solution of 11.8 g.
Al(H2P04)3 i.n 13.2 grams ~I20. 11.0 g. of spinel sintered at ~1600C was added and -the slurry se-t aside. In a separate container 75 grams of a mixture produced by ball milling 30 g of dolomite (MgCa(C03)2) -together with lO0 grams of magnesium aluminum spinel sintered at
2 ~1600C was slurried in 20 grams H2O. The two slurries are mixed and immediately react, with CO2 gas being generated by the action of the acidic aluminum phos-phate on the dolomite. The product expands by a factor of 2 in volume, and sets in about 4 minutes. After firing, it has a density of 0.66 g/cm3 (41 lb/ft3).
This material is especially useful as a back-up refrac-tory foamed in place to fill unusual, irregular, or difficult to access spaces.
Magnesium aluminum spinel, 120 grams, cal-cined a-t 1600C was mixed with 40 grams sintered Al2Oa then added to a solution of 35 grams of 85% H3PO~, and 32,775 F -7_ . . .
~2~
10 grams water. Thereafter 50 grams of Mg2A13(OH)4.5 -(HC03)o.5 was slurried in 60 grams of water. The two slurries were mixed and the volume doubled. The mixture set in about 4 minutes.
In each case the compositions are flred to a temperature of at least 200C.
This material is especially useful as a back-up refrac-tory foamed in place to fill unusual, irregular, or difficult to access spaces.
Magnesium aluminum spinel, 120 grams, cal-cined a-t 1600C was mixed with 40 grams sintered Al2Oa then added to a solution of 35 grams of 85% H3PO~, and 32,775 F -7_ . . .
~2~
10 grams water. Thereafter 50 grams of Mg2A13(OH)4.5 -(HC03)o.5 was slurried in 60 grams of water. The two slurries were mixed and the volume doubled. The mixture set in about 4 minutes.
In each case the compositions are flred to a temperature of at least 200C.
Claims (9)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A composition comprising:
(a) 10 to 80 percent by weight of a reactive MgA12O4 spinel or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures, and prepared by water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
(b) A non-reactive gas autogenerated from 1 to 40 percent by weight of a compound which decomposes under acidic conditions and generates a gas within said composition;
(c) L to 20 percent by weight of an inorganic phosphorous compound which forms (PO3)3 moities on heating at above about 200°C; and (d) 8 to 40 percent by weight of water.
(a) 10 to 80 percent by weight of a reactive MgA12O4 spinel or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures, and prepared by water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
(b) A non-reactive gas autogenerated from 1 to 40 percent by weight of a compound which decomposes under acidic conditions and generates a gas within said composition;
(c) L to 20 percent by weight of an inorganic phosphorous compound which forms (PO3)3 moities on heating at above about 200°C; and (d) 8 to 40 percent by weight of water.
2. A composition as claimed in claim 1, which also comprises a substantially non-reactive filler in an amount of up to 50 percent by weight of the composition.
3. A composition as claimed in claim 1, which also comprises a handling agent, in an amount of up to 5 percent of the composition.
4. A composition as claimed in claim 1, 2 or 3, wherein said MgA12O4 of component (a) is a mixture of a first spinel which has been calcined to about 900°C and a second spinel which has been calcined to about 1600°C.
5. A composition as claimed in claim 1, 2 or 3, wherein the phosphorous compound is Al(H2PO4)3.
6. A composition as claimed in claim 1, 2 or 3, wherein the gas producing compound is dolomite.
7. A composition as claimed in claim 1, 2 or 3, wherein the MgA12O4 of component (a) has been calcined to 1600°C, the phosphorous compound is H3PO4 and the gas producing compound is MgAl(OH)4.5(HCO3)0.5.
8. A process for producing a porous refractory composition, which process comprises forming an aqueous suspension comprising:
(a) 10 to 80 percent by weight of a reactive spine]. or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures and prepared by coprecipitating water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
(b) from 1 to 40 percent by weight of a compound which decomposes under acidic conditions to form a gas;
(c) 1 to 20 percent by weight of an inorganic phosphorous compound which forms (PO3)3 moieties on heating at above about 200°C; and (d) 8 to 40 percent by weight of water, and allowing the components to react to form a porous refractory composition.
(a) 10 to 80 percent by weight of a reactive spine]. or mixture of reactive MgA12O4 spinels which have been calcined to different temperatures and prepared by coprecipitating water-soluble magnesium and aluminum salts in a proportion to provide about 1 magnesium atom per 2 aluminum atoms;
(b) from 1 to 40 percent by weight of a compound which decomposes under acidic conditions to form a gas;
(c) 1 to 20 percent by weight of an inorganic phosphorous compound which forms (PO3)3 moieties on heating at above about 200°C; and (d) 8 to 40 percent by weight of water, and allowing the components to react to form a porous refractory composition.
9. A process for making fired refractory material, which process comprises forming a porous refractory composition by a method as claimed in claim 8, and subsequently firing the composition.
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Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US65915584A | 1984-10-09 | 1984-10-09 | |
| US659,155 | 1984-10-09 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1236491A true CA1236491A (en) | 1988-05-10 |
Family
ID=24644270
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000491910A Expired CA1236491A (en) | 1984-10-09 | 1985-09-30 | Low density phosphate bonded spinel refractories |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0178837A3 (en) |
| JP (1) | JPS61117175A (en) |
| AU (1) | AU576266B2 (en) |
| BR (1) | BR8504989A (en) |
| CA (1) | CA1236491A (en) |
| DK (1) | DK459785A (en) |
| FI (1) | FI853932L (en) |
| NO (1) | NO853971L (en) |
| ZA (1) | ZA857746B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0187491U (en) * | 1987-11-27 | 1989-06-09 | ||
| US5691257A (en) * | 1995-07-19 | 1997-11-25 | Corning Incorporated | Low density cellulated body and method |
| JP5877821B2 (en) * | 2013-08-12 | 2016-03-08 | クアーズテック株式会社 | Composite fireproof insulation |
| JP6841817B2 (en) * | 2015-09-09 | 2021-03-10 | サソール（ユーエスエイ）コーポレーシヨン | Manufacturing method of magnesium aluminate spinel |
| CN115340362A (en) * | 2022-08-30 | 2022-11-15 | 宜兴市耐火材料有限公司 | Alumina fiber reinforced magnesia carbon sliding plate and preparation process thereof |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3730744A (en) * | 1970-08-31 | 1973-05-01 | Basic Ceramics Inc | Aluminum phosphate bonded refractory and method for making the same |
| US4394455A (en) * | 1980-12-18 | 1983-07-19 | The Dow Chemical Company | Spinel slip casting composition and articles |
| CA1186130A (en) * | 1981-06-16 | 1985-04-30 | Jeffery L. Barrall | Rigid, water-resistant phosphate ceramic materials and processes for preparing them |
| US4439532A (en) * | 1981-08-26 | 1984-03-27 | The Dow Chemical Company | Casting slip made from spinel and spinel refractories |
| US4459156A (en) * | 1982-12-20 | 1984-07-10 | The Dow Chemical Company | Phosphate bonding of reactive spinels for use as refractory materials |
-
1985
- 1985-09-30 CA CA000491910A patent/CA1236491A/en not_active Expired
- 1985-10-02 AU AU48200/85A patent/AU576266B2/en not_active Ceased
- 1985-10-08 EP EP85307188A patent/EP0178837A3/en not_active Withdrawn
- 1985-10-08 NO NO853971A patent/NO853971L/en unknown
- 1985-10-08 ZA ZA857746A patent/ZA857746B/en unknown
- 1985-10-08 BR BR8504989A patent/BR8504989A/en unknown
- 1985-10-08 DK DK459785A patent/DK459785A/en not_active Application Discontinuation
- 1985-10-09 JP JP60223863A patent/JPS61117175A/en active Pending
- 1985-10-09 FI FI853932A patent/FI853932L/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0178837A2 (en) | 1986-04-23 |
| JPS61117175A (en) | 1986-06-04 |
| EP0178837A3 (en) | 1987-04-08 |
| FI853932A0 (en) | 1985-10-09 |
| BR8504989A (en) | 1986-07-29 |
| DK459785D0 (en) | 1985-10-08 |
| FI853932L (en) | 1986-04-10 |
| DK459785A (en) | 1986-04-10 |
| AU4820085A (en) | 1986-06-12 |
| NO853971L (en) | 1986-04-10 |
| ZA857746B (en) | 1987-06-24 |
| AU576266B2 (en) | 1988-08-18 |
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